Over the past several years, the detergent market has shifted towards heavy-duty liquid (HDL) laundry detergents. Whilst much of this shift is driven by the pre-dissolved nature of the HDL detergent product, which eliminates the occasional occurrence of undissolved or partially-dissolved residues on fabrics associated with granular laundry detergents, HDL detergents offer the laundry detergent formulator more freedom and flexibility to use solution-based precursors in the formulation, especially water-soluble and/or water-dispersible polymers. The chemistries of said water-soluble and/or water-dispersible polymers have evolved over the past decade to deliver improved detergent performance, especially with regard to builder functionality and soil dispersion. In addition, there may be additional functionalities that can be specially developed for granular detergents using polymers: e.g. chelating heavy metals that can otherwise interfere with bleach chemistry. Based on this performance evolution, it has become increasingly desirable to include higher levels of water-soluble precursors in granular detergents.
Generally, there are two primary types of processes by which detergent granules or powders can be prepared. The first type of process involves spray-drying an aqueous detergent slurry in a spray-drying tower to produce highly porous detergent granules (e.g. a tower process for the production of low density detergent compositions). In the second type of process, the various detergent components are dry mixed after which they are agglomerated with a binder such as a nonionic or anionic surfactant, to produce high density detergent compositions (e.g. an agglomeration process for the production of high density detergent compositions).
Additionally, extrusion processes have been used to make detergent particles using a combination of dry powder and liquid binder components, similar to agglomeration processes.
In the above processes, the important factors which govern the density of the resulting detergent granules are the shape, porosity and particle size distribution of said granules, the density of the various detergent adjunct ingredients, the shape of the various detergent adjunct ingredients, and their respective chemical composition. Of the above processes, it is considered that spray-drying is well suited to handling large formula fractions of solution-based precursors.
However, there are several issues with spray-drying that render it unsuitable to produce the desired end products. Also, there is still a need to improve the solubility of granular detergent products. Thus, there is still a need for developing a process for making detergent granules, which is suitable to produce the desired end products.